I don't even know what Longshot is, but it sounds like a slow burning powder for heavy loads, explaining the poor combustion. A 1 1/8 ounce ten gauge load would seem to call for a fast powder like the Red Dot (maybe 19 or 20 grains) that you probably have 30 pounds of in the house somewhere. An even faster powder like Bullseye would probably also work in very light ten loads.